isAsyncFunction

Checks if the given argument is an async function.

Use Object.prototype.toString() and Function.prototype.call() and check if the result is '[object AsyncFunction]'.

const isAsyncFunction = val =>
  Object.prototype.toString.call(val) === '[object AsyncFunction]';

isAsyncFunction(function() {}); // false
isAsyncFunction(async function() {}); // true

Last updated 15 September 2026 · Edit this page